Extreme UV single crystal diamond photodetectors by chemical vapor deposition

The detection properties of a UV photodetector realized on a 150 mu m thick CVD single crystal diamond film, grown at Roma "Tor Vergata" University on a low cost HPHT diamond substrate, are reported. The device was tested in the 210 - 2400 nm spectral range using pulsed laser irradiation and in the 20 - 250 nm range in continuous mode by both a deuterium lamp and a helium DC gas source irradiation. The detector shows more than five orders of magnitude of visible/UV rejection ratio, a very sharp signal drop of about 104 being observed in correspondence of the diamond energy gap. In the extreme UV range, the He II 25.6 and 30.4 nm as well as the He I 58.4 nm emission lines are clearly detected. The diamond time response is demonstrated to be considerably lower than 5 ns and 0.2 s in pulse and continuous mode, respectively. The extremely good signal to noise ratio, stability and reproducibility of the device response obtained, indicate that no persistent photoconductivity nor undesirable pumping effects are present, which represented so far the main problems preventing the use of diamond based detectors for UV applications.